The application of labels to products or parts moving along a conveyor line is a process that is widely used in industry. Generally, the labels are contained and stored on a long continuous strip of webbing or backing material that is wound on a reel mounted on a labeler. When the reel is rotated, a label to be applied is peeled off of its backing strip and held or suspended on a grid plate by a partial vacuum. A part sensor located either on the conveyor or the labeler detects the presence of a part under the suspended label. After a short time delay, a positive air pressure is applied to the back of the label; and it is blown off of the grid plate onto the product.
While there are many different types and varieties of labeling machines, of particular interest is the model 2111-ST labeler manufactured by Label-Aire Inc. and commercially available from the Label-Aire Division of Wallace Computer Services, Inc. of Indianapolis, Ind. With that labeling machine, the strip of backing material containing the labels is fed over an upper surface of a peeler plate, over a peeler plate edge and then, back along a path generally adjacent a lower surface of the peeler plate. The backing material is typically more flexible than the labels attached thereto; and therefore, the backing material readily bends around the peeler plate edge. The label being of a stiffer material will resist bending around the edge of the peeler plate and begin to separate from the backing material strip as the feeding action or motion of the backing material strip continues.
The label continues to feed in a generally horizontal direction beneath a grid plate. The grid plate is perforated by a pattern of holes which are in fluid communication with a plenum above the gird plate having a negative pressure with respect to atmospheric pressure, that is, a partial vacuum. The partial vacuum is normally created by a fan that pulls air through the grid plate holes, thereby creating a suction force on the bottom surface of the grid plate to suspend or hold the label thereon. The feed of the backing material strip continues until the label is completely separated therefrom and is held by the suction force on the grid plate.
The labeling machine is positioned with respect to a moving conveyor line such that a part sensor mounted on the conveyor or the labeler defines a label application position with respect to the suspended label. When the part is at that position, air under a positive pressure is blown through tubes connected to selected ones of the holes on the top side of the grid. The fluid pressure through the tubes is sufficient to overcome the vacuum created by the fan, and the label is blown off of the bottom of the grid and onto the part on the conveyor line.
The operation of the above described labeling machine has proven to be satisfactory in the application of labels to products, for example, plastic cases in which CD's are packaged. In the normal course of a packaging process, the labels being applied to the products may change, or the products themselves may change, thereby requiring different labels. When a different size label is to be used, the labeling machine must be set up for the new label. With each different size label, the application of the pressurized fluid through the holes in the grid must be adjusted. The grid is manufactured to a size accommodating the largest label that the labeling machine will accept. Therefore, the grid may have an area of four or more inches on a side. Further, with each different size label, the suction and blow off forces through the bottom of the grid must be adjusted to most effectively hold and then subsequently blow the label onto the part.
To initially set up the above-described labeling machine, a cover forming a plenum on top of the grid hole is removed. Next, a masking plate is put in place on top of the grid plate so that it covers all of the holes. By viewing down the edge of the grid plate that receives the label, a sample label is located on the upper surface of the masking plate so that it overlies the location of a production label on the lower surface of the grid plate. The masking plate is then removed from the grid plate; and using the sample label as a template, an opening is cut in the masking plate to correspond to the size of the sample label. After the label-shaped hole in the masking plate is cut, the masking plate is again mounted on the upper surface of the grid so that the holes outside of the perimeter of the label cut-out are covered.
The positive pressure to blow the label off of the bottom of the grid plate is adjusted by locating a plurality, for example, 18, flexible tubes having a one end connected to a manifold. The other, distal ends of the tubes are inserted into selected ones of the uncovered holes in the top of the grid plate such that the label is most effectively held on and then subsequently blown off the grid plate. The number and location of the tubes will depend on the area of the label, the label material and thickness. Preferably, more tubes are used in a pattern at the center of a label with fewer tubes being located with respect to the label periphery.
The cover plate providing a plenum for the vacuum fan is then put in place over the grid plate, and the labeling machine is ready for testing. Therefore, the vacuum or suction from the fan is limited to those holes which are not covered by the masking plate and those holes to which pressure tubes are not connected. The placement of the tubes can be time-consuming process, especially the first time that a label is used. Once a proper tube placement is determined, it can be recorded for future reference.
Several test labels are then run through the labeling machine and applied to the part on the conveyor to test the setup of the machine. When working with new labels which have not previously been used, and for which the appropriate location of the pressure tubes is not known, the initial placement of the pressure tubes may result in the label not being applied to the desired location on the part. In other situations, the location of the pressure tubes may result in the position of successive labels varying beyond an acceptable tolerance. Ideally, each label should be applied at precisely the same relative location on each product or case on the conveyor line. If the labels are not being applied to the proper location or the label is being applied inconsistently, that is, the label is not being repeatably applied at the same location on the part, a portion of the set up procedure must be repeated. For example, at the least, the plenum cover must be removed in order to relocate the pressure tubes, and then the plenum cover is reinstalled. The above process is repeated until a pattern of pressure tube locations is found that provides the desired accuracy and consistency in the label placement.
Consequently, there is a need for a label handling system for a labeling machine that permits a faster set up procedure.